1. Field of the Invention
The present invention relates to a control apparatus for a hybrid vehicle, which is equipped with an internal combustion and an electric motor as the power source of a vehicle.
2. Description of Related Art
As this type of apparatus, there has been suggested an apparatus of performing rotation synchronization and position synchronization by feedback control on a dog clutch which can be applied to a hybrid vehicle (e.g. refer to Japanese Patent Application Publication Laying Open No. 2005-278225). According to the rotating-body control apparatus and method disclosed in Japanese Patent Application Publication Laying Open No. 2005-278225 (hereinafter referred to as a “conventional technology”), switching over from feed-forward control to feedback control is performed on the basis of the judgment of whether or not it can be controlled in a target rotation status by a control model. Thus, the rotation status of a rotating body is considered to be easily controlled in the target rotation status on the basis of the control model.
Incidentally, there has been also suggested a technology in which motor control is performed on the basis of the variation of a duty value outputted by a feedback controlling device to an inverter in the low-speed rotation of a motor (e.g. refer to Japanese Patent Application Publication Laying Open No. Hei 9-308281).
Moreover, there has been also suggested such a technology that in a hybrid vehicle in which the number of revolutions of an engine is derived from the numbers of revolutions of a drive motor and a generator, if an abnormality of a generator resolver is detected, the number of revolutions of the engine is derived using a pulse from a crank shaft (e.g. refer to Japanese Patent Application Publication Laying Open No. 2001-171369).
Moreover, there has been also suggested such a technology of performing the feedback control by estimating the number of revolutions, instead of a number-of-revolutions-sensor (e.g. refer to Japanese Patent Application Publication Laying Open No. 2001-1779).
Moreover, there has been also suggested a transmission system of performing feedback by the number-of-revolutions-sensor (e.g. refer to Japanese Patent Application Publication Laying Open No. 2004-525326).
If a target rotational speed for a control target is in a relatively low area such as zero rotation, detection accuracy of the rotational speed of a rotating-body at the current time point, which is referred to in determining a feedback control amount associated with the feedback control near the target rotational speed, is possibly reduced. If the detection accuracy is reduced, even if the control model correctly functions, the rotation status of the rotating body possibly does not correctly move into the target rotation status. In particular, if the rotating body as the control target requires correct rotation control and position control such as a dog clutch, there may be troubles, for example, such as oscillation and noise in engaging dog teeth, in the situation lacking the control accuracy as described above. The occurrence of the troubles may actualize a reduction in drivability or reliability in the hybrid vehicle if these rotating bodies are mounted on the hybrid vehicle. In other words, the conventional technologies hardly avoid the reduction in drivability or reliability in the hybrid vehicle, due to the reduction in the detection accuracy of the rotational speed of the rotating body, which is technically problematic.